Keyboard using switches having light obstructing elements

ABSTRACT

Keyboard apparatus for producing switch signal combinations in a code used in office machines includes a number of individual light beam producing means corresponding in number to the number of channels used in the code, and a number of individual keys, each of which carries one or more light-obstructing barriers, the number and position of the barriers on a particular key corresponding to the number and position of the channels used in the machine code system to indicate the signal combination associated with the key so that when a key is depressed the light beams will be selectively interrupted to thereby form a coded signal representing the depressed key.

United States Patent [72] lnventors Konrad Sturm Nurnberg; Willy Becker,Behringersdorf; Heinz Timm, Brunn; Karlheinz Rummel,

Nurnberg, Germany [21] Appl. No. 798,881 [22] Filed Feb. 13, 1969 [45]Patented May 18, 1971 [73] Assignee Firma Diehl Nurnberg, Germany [32]Priority Feb. 13, 1968 [33] Germany [31] P 15 74 554.7

[S4] KEYBOARD USING SWITCHES HAVING LIGHT Primary Examiner-James W.Lawrence Assistant Examiner-Martin Abramson Attorney-Spencer & KayeABSTRACT: Keyboard apparatus for producing switch signal combinations ina code used in office machines includes a number of individual lightbeam producing means corresponding in number to the number of channelsused in the code, and a number of individual keys, each of which carriesone or more light-obstructing barriers, the number and position of thebarriers on a particular key corresponding to the number and position ofthe channels used in the machine code system to indicate the signalcombination associated with the key so that when a key is depressed thelight beams will be selectively interrupted to thereby form a codedsignal representing the depressed key.

Patented May18, 1971 3,579,047

4 Sheets-Sheet 1 INVENTORS: Konrad STURM Willy BECKER Heinz T/MMKarlheinz RUMME L 3 a pwwr, Q our;

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INVENTORS' Konrad STURM W/{Iy BECKER Heinz TIMM Karlheinz RUMMEL 5" v pw 'n 11 HELormgs Patented May 18, 1971 4 Sheets-Sheet 5 Fig.

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FLlP-FLOPS INVENTORS: Konrad STURM Willy BEC Heinz TIMM Karlheinz RUMMEL Rktomegs 4 Sheets-Sheet 4 5 RE SISTORS 16 2Qo- FH' h RESISTOR 19 Hun 5E RESISTOR Fig. 6

INVENTORS: Konrad STURM Willy BECKER Heinz TIMM Karlheinz RUMMEL 35y 2Roud Rthornegs KEYBOARD USING SWITCHES HAVING LIGI-IT OBSTRUCTINGELEMENTS BACKGROUND OF THE INVENTION 1. Field of the Invention Thisinvention relatesto office machines and more particularly to a keyboardarrangement for producing signal combinations in the code system used inmachines which are associated with the respective key.

2. Description of the Prior Art The German published patent application(DAS) 1,197,934 discloses a ten-key keyboard for telephone installationsin which a light barrier is interrupted by depressing a key and thus aswitching criterion is produced. In order not to require a separatelight barrier for each key of this ten-key keyboard, the knownarrangement employs a coordinate arrangement of the light barriers withwhich it is possible to produce output signals with a total of sevenlight barriers.

In this known keyboard it is necessary, if it is to be used in a machineoperating with a code, to additionally provide a coding device whichconverts the signals from the light barriers into signals according tothis machine code.

it is the object of the present invention to provide a keyboard whichmakes possible, with as low a number of light barriers as possible, theemission of a substantially lower number of switching signals than theknown keyboard and which requires only a few coding means.

' SUMMARY or THE INVENTION Among the objects of the present invention isthe provision of keyboard apparatus which produces signal combinationsindicative of the particular key in the machine code system used whichrequires a minimum of switching signals, elements and coding means.

A further object is the provision of such apparatus which is reliable inoperation.

A further object is the provision of such apparatus which is expensiveto manufacture and permits generous production tolerances, and which canbe operated with a minimum of finger pressure.

Briefly stated, these and other objects are achieved by the provision ofa plurality of light paths whose interruption upon operation of a keyinitiates the switching signals. Moreover, a mechanical switching ortriggering element is associated with each key in such a manner that,upon operation of a key, one or a plurality of the existing light pathsare interrupted corresponding to the particular code used in the machineand that the pulse or corresponding pulses, respectively, represent thesignal combination associated with the respective key.

According to a further development of the present invention, aplurality, e.g. a total of six, light paths corresponding in number tothe number of channels in the machine code system. At one end areprovided with each of these paths having a light source at one end and aphotoelectric receiving element, particularly a photodiode, at the otherend thereof and the mechanical switching elements are arranged such thateach light path can be blocked by a plurality of such-mechanicalswitching elements. It is particularly advantageous to arrange thesepaths alongside each other and to provide the switching elementassociated with a particular key with one or a plurality oflight-obstructing barriers each of which is moved into one of theselight paths when the respective key is operated i.e. depressed.

The present invention thus is based on a construction in which aplurality of paths along which a light beam passes are arranged adjacenteach other and a mechanical switching element is operated by a key, theparticular configuration of this switching element with respect to themachine code employed being such as to enable it to block or close oneor simultaneously a number of these light paths. If, for example, a codehaving n channels is used where n equals 6, this means that oneswitching element is able to close at least one path or a maximum of allsix light paths. With this code, a total of 63 switching signalcombinations can be produced and it is thus possible to employ up to 63keys in a keyboard while using only six light paths. Since the codeemployed in the keyboard is the same as that of the machine, furthermeans for converting the signals to the machine code are unnecessary.

The present inventionthus provides a keyboard in which easy operabilityby slight finger pressure is combined with an extremely low requirementfor switching elements.

According to a particularly advantageous further develop ment of thepresent invention, it is proposed to provide a further, i.e. a seventh,light path into which a further light obstructing barrier on each of themechanical switching or triggering elements moves. This further lightobstructing barrier interrupts its associated light path somewhat laterthan the other light-obstructing barriers of the same triggeringelement. An electric AND circuit is provided in which the output signalsof all light paths are logically linked in such a manner that a signalis produced at the output of the AND circuit only when a signal from oneor more of the light paths corresponding to machine code channels and asignal from the seventh light path are present at the same time.

With this further development of the present invention, a switchingsignal is emitted only when all light paths corresponding to signalcombinations-associated with the respective key are definitely closed.This permits generous production tolerances for guiding the switchingelement as well as for the light-obstructing barriers themselves Thisresults in a reduction in production costs.

It is, moreover, desirable to construct each keys mechanical element asa flat piece which is mounted for parallel movement. Such a fiat piececan be manufactured in a simple manner as by stamping.

BRIEF DESCRIPTION OF THE DRAWINGS 1 DESCRIPTION OF A PREFERREDEMBODIMENT In FIG. 1, a large number of keys 2 are arranged on a board1, the keys being attached to key shafts or connectors 3 which extendthrough openings in the board 1. Below the board 1 there are a total ofseven light paths or ducts 4, which are marked individually as 41 to 47.A bank 5 of light sources 51 to 57 is provided at-one end of the ducts4, a bank of photoelectric receiving elements 61 to 67, e.g., aflip-flop incorporating a light-sensitive member, is provided at theother end of the ducts 4 with one light source and one receiving elementbeing associated with each of the ducts 41-47 respectively. Each keyconnector 3 forms the upper part of a mechanical switching element 7constructed as a flat piece and extending underneath board 1 over itsentire width and being provided, at its side away from the board, withat least two, but with a maximum of seven light-obstructing barriers ortabs 71 to 77 (FIG. 2) which can dip into the light paths or ducts 41 to47 respectively. At the switching element 7 disposed up front there are,for example, six obstructing barriers, the barrier which would dip intolight duct 42 being missing. The arrangement of these light barriers ortabs on switching element 7 is made according to a (nQcode where nequals 1 to 6. The barrier 77 of each switching element 7, which dipsinto light duct 47, is somewhat shorter than the other barriers for thepurpose of closing duct 47 only after'it has been definitely establishedthat one or 'a plurality of ducts 41 to 46 have'been closed by therespective barriers 71 to 76. An output signal is considered to bepresent only when duct 47 is also closed. This has the advantage that noparticularly high demands need be placed on the tolerances for therespective dimensions in the manufacture of the switching element 7 andits tabs since it does not matter whether paths 41 to 46 are closedexactly at the same time or not.

Each switching element 7 is preferably provided with a short arm memberor shaft 8 at its left end extends up through a slot in the board 1 andwhich serves to parallel-guide the switching element. Those keys, whichare arranged at the left edge of the board and in which this left armmember must serve as the key shaft 3, are provided at their right sidewith an arm member 8 which serves for parallel-guiding instead of shaft8. For the purpose of good parallel-guiding there are also provided twokey shafts 3 for particularly large keys, as for example the addition ormultiplication keys, etc. Such an arrangement of two key shafts 3 can beseen, for example, at the first switching element 7 in FIG. 1. Theimportant element for parallel-guiding a switching element 7, however,is the vertical guide member 9 which slides in a guide groove not shownin the drawing for reasons of clarity.

The keys are operated against the force of a spring 10. In order toprevent a second key from being depressed before the previouslydepressed key has returned to its initial or rest position, a ball cage11 is provided. Each switching element 7 has a tongue 12 which dipsbetween two balls of the ball cage 11 when the key is being operated.This pushes all the adjacent balls toward the left and right so thatthese balls come to lie so closely together, due to the low amount ofplay provided, that tongue 12 of another switching element 7 can nolonger dip into the ball cage.

The upper edge of tongue 12 and the edge 13 of the same switchingelement 7 facing this tongue serve to limit the upward and downwardmovement of the switching element 7 in cooperation with a flap 15 ofsynthetic material which is placed around the frame portion 14.

FIG. 2 shows a switching element 7 in an enlarged view. The shorterbarrier 77 for duct 47 is here disposed on the extreme right. It is, ofcourse, also possible, within the sense of the present invention, toarrange the light ducts and barriers in a different way and particularlyto dispose barrier 77 and light duct 47, for example, between the otherbarriers 71 to 76 or ducts 41 to 46. A particularly suitable arrangementis shown in FIG. 3 in which some of the barriers are disposed to theleft and others to the right of the vertical guide member 9. Thisarrangement has the particular advantage that the torque applied to thevertical guide member 9 due to the asymmetry of the switching element iskept as low as possible.

FIG. 4 shows a schematic circuit diagram of the electric circuitry, thearrangement of the ducts as well as the position of the respectiveoutput signals. To the outputs of all photoelectric receiving elements61-67, which are provided in the form of photodiodes, a total of sevenamplifiers and inverter circuits 16 are connected at whose outputsappear the signal combinations 17, e.g., LLOOOOL, including the signalfrom light path 47. The photoamplifiers are here so constructed that thesignals emitted from the photodiodes are inverted so that when one ofthe duct 4 is darkened or closed a signal is present at the output ofthe respective photoamplifier, whereas when a duct 4 is not closed, nosignal is present at the output of the respective photoamplifier 16. Thesignals shown under 17 appear during the time when the respective ducts4 are closed. This interval is somewhat shorter than the time duringwhich the key is being operated. It can be clearly seen that in lightduct 47 the corresponding output signal is substantially shorter thanthat in ducts 41 and 42. To the outputs of photoamplifiers 16 isconnected a logic circuit 18 consisting of individual AND circuits 81 to86 which are so interconnected that a transmission of the signals fromducts 41 to 46 is only possible when the signal from duct 47 is alsopresent.

Thus the normed signals of ducts 41 to 46 appear at the output of thislogic circuit 18.

FIG. 5 shows a particularly advantageous further development of thepresent invention in which phototransistors are used as photoelectricreceiving elements instead of photodiodes, which phototransistors arepart of a normal bistable flip-flop. Instead of a bistable flip-flop itis also possible to use a Schmitt trigger or a circuit arrangement .withsimilar switching characteristics. W hen the appropriate light duct 41to 47 is closed, the phototransistor of the corresponding flip-flop 61to 67 is blocked and thus the bistable flip-flop is put into oneswitching state. The resulting output signals of the seven light pathsare further evaluated in the manner already described in the circuit 16.This arrangement has the advantage that the switching signal is presentindependent of the length of the time the key is operated. Since thephototransistors can emit a new signal only after the associatedflip-flop has been reset, a resetting pulse is fed in on line 19. Such aresetting pulse may be derived at any suitable place in the machine.

The term light" employed in the above description is not limited tovisible light but is intended to apply to any other suitable radiationnot discernible to the human eye.

Circuits with phototransistors or other light activated switches arewell known to those skilled in the art. For example such circuits aredisclosed in lntemational Electroncs, July 1964, pages 49 to 53,especially FIG. 5c.

If a normal NPN-transistor is substituted for one of the twolight-activated elements in such a circuit as it is shown in FIG. 6 ofthe drawings, the resulting bistable flip-flop satisfies therequirements of an element 6 of FIG. 5. The bistable flip-flop is set bya signal from a light source 5 at element LAT and it is reset by asignal on line 19, which is fed to the base of transistor T.

A normal timing circuit 20 in the machine, which is activated by thesignal on duct 47, generates the reset signal for flip-flops 61 to 67 online 19 after a predetermined period of time-for example 40 msec.'thissignal switching over transistor T and preparing element LAT of everyflip-flop 61 to 67 for the next switching operation. The activatingsignal for timing circuit 20 can be take off the input of flip-flop 67,this input, for example, being point 20 of a flip-flop like FIG. 6. Theaforesaid period of time is determined by the time necessary forprocessing the data in the office machine, which was delivered on therespective key.

It will be readily apparent that there has been provided a keyboardcircuit arrangement for producing signal combinations which areindicative of the particular key in the machine code used which requiresa minimum of switching elements, is reliable in operation, inexpensiveto manufacture, permits generous production tolerances and'requiresminimum finger pressure. 7

It will be understood that the above description of the presentapplication is susceptible to various modifications, changes andadaptations.

We claim:

l. A keyboard apparatus for producing signal combinations indicative ofparticular keys in a multichannel office machine code system in whicheach channel may carry a signal, and particular keys are represented bythe presence of signals on particular designated channels, the apparatuscomprising, in combination:

a. support means;

b. means for producing a plurality of light beams equal in number to thenumber of channels in the machine code system;

c. a like plurality of photoelectric receiving means, one for each ofsaid light beams, arranged in designated positions on the support meansfor producing signals in respective ones of said channels in response toa. change in the detected radiation;

d. a plurality of key members larger in number than said plurality oflight beams, each of said key members being mounted on said supportmeans. for movement relative thereto from a rest position to a depressedposition, each of said key members including means for selectivelyinterrupting one or more of said light beams in accordance with themachine code associated with the respective key when said respective keyis depressed, whereby the combination of the signals produced by saidplurality of photoelectric receiving means as a result of the depressionof a key is a coded representation of the depressed key.

2. The keyboard apparatus as defined in claim 1 including a plurality oflight ducts, one for each of said light beams, mounted on said supportstructure, each of said light ducts having a respective one of saidlight beam producing means at one end thereof and a respective one ofsaid photoelectric receiving means at the other end thereof; and whereinsaid means for selectively interrupting said light beams includes anumber, from one to the number of said light beams, of lightobstructingtabs mounted on each key member for movement therewith, each of saidtabs being positioned relative to said ducts so that upon depression ofthe respective key each of said tabs will extend into a respective oneof said ducts and block the light beam passing therethrough.

3. Apparatus as defined in claim 2 wherein each of said photoelectricreceiving means is a photosensitive semiconductor device.

4. Apparatus as defined in claim 2 wherein said light ducts and theirassociated light beam producing means and photoelectric receiving meansare so positioned that the respective light paths are substantiallyparallel to each other.

5. Apparatus as defined in claim 4 including an additional light beamproducing means and an associated photoelectric receiving means mountedon said support means to provide an additional light path which issubstantially parallel to the other light paths; and wherein each keymember carries an additional light obstructing tab means positioned onsaid key member for blocking the said additional light path at asomewhat later time during the movement of the key to said depressedposition than the other tabs block their respective 6. Apparatus asdefined in claim 2 wherein each key member comprises a fiat memberhaving said light obstructing tabs extending from the body thereof andwherein the individual keys are mounted on said support means parallelto each other for movement in the plane defined by the flat body.

7. Apparatus as defined in claim 6 wherein eachflat key member includesa guide member extending in the plane of the flat member and carryingtwo abutments for limiting its movement in opposite directions.

8. Apparatus as defined in claim 1 including means for preventing thedepression of any key while another key is depressed.

9. Apparatus as defined in claim 8 wherein said means for preventingdepression of any key while another key is depressed comprises: a ballcage means including a channel having stops at each end and a number ofballs disposed therebetween, tongue means on each key member positionedfor movement between individual balls upon movement of the key to thedepressed position, the dimensions of said channel, its stop means andsaid balls being such that only one tongue means can fit between theballs at a time.

10. Apparatus as defined in claim 3 wherein each of said photosensitivesemiconductor devices is a phototransistor which is a part of arespective bistable flip-flop circuit and which causes the respectiveflip-flop circuit to assume its set condition when the respective lightbeam is interrupted upon depression of a key; and 'wherein means areprovided for generating a reset pulse for said flip-flop circuits.

. 11. Apparatus as inclaim 10 including means for blocking theunoperated key means in response to the output signal of thesetflip-flop circuit. I

- l2. Appara us as defined lll claim 1 m which the machine code systemuses six digits and there are six light beams and six outputsignal-producing means.

1. A keyboard apparatus for producing signal combinations indicative ofparticular keys in a multichannel office machine code system in whicheach channel may carry a signal, and particular keys are represented bythe presence of signals on particular designated channels, the apparatuscomprising, in combination: a. support means; b. means for producing aplurality of light beams equal in number to the number of channels inthe machine code system; c. a like plurality of photoelectric receivingmeans, one for each of said light beams, arranged in designatedpositions on the support means for producing signals in respective onesof said channels in response to a change in the detected radiation; d. aplurality of key members larger in number than said plurality of lightbeams, each of said key members being mounted on said support means formovement relative thereto from a rest position to a depressed position,each of said key members including means for selectively interruptingone or more of said light beams in accordance with the machine codeassociated with the respective key when said respective key isdepressed, whereby the combination of the signals produced by saidplurality of photoelectric receiving means as a result of the depressionof a key is a coded representation of the depressed key.
 2. The keyboardapparatus as defined in claim 1 including a plurality of light ducts,one for each of said light beams, mounted on said support structure,each of said light ducts having a respective one of said light beamproducing means at one end thereof and a respective one of saidphotoelectric receiving means at the other end thereof; and wherein saidmeans for selectively interrupting said light beams includes a number,from one to the number of said light beams, of light-obstructing tabsmounted on each key member for movement therewith, each of said tabsbeing positioned relative to said ducts so that upon depression of therespective key each of said tabs will extend into a respective one ofsaid ducts and block the light beam passing therethrough.
 3. Apparatusas defined in claim 2 wherein each of said photoelectric receiving meansis a photosensitive semiconductor device.
 4. Apparatus as defined inclaim 2 wherein said light ducts and their associated light beamproducing means and photoelectric receiving means are so positioned thatthe respective light paths are substantially parallel to each other. 5.Apparatus as defined in claim 4 including an additional light beamproducing means and an associated photoelectric receiving means mountedon said support means to provide an additional light path which issubstantially parallel to the other light paths; and wherein each keymember carries an additional light obstructing tab means positioned onsaid key member for blocking the said additional light path at asomewhat later time during the movement of the key to said depressedposition than the other tabs block their respective light paths; andlogic circuit means for producing an output signal only when a signalfrom at least one of the first-mentioned photoelectric sources and asignal from said additional photoelectric light source aresimultaneously present.
 6. Apparatus as definEd in claim 2 wherein eachkey member comprises a flat member having said light obstructing tabsextending from the body thereof and wherein the individual keys aremounted on said support means parallel to each other for movement in theplane defined by the flat body.
 7. Apparatus as defined in claim 6wherein each flat key member includes a guide member extending in theplane of the flat member and carrying two abutments for limiting itsmovement in opposite directions.
 8. Apparatus as defined in claim 1including means for preventing the depression of any key while anotherkey is depressed.
 9. Apparatus as defined in claim 8 wherein said meansfor preventing depression of any key while another key is depressedcomprises: a ball cage means including a channel having stops at eachend and a number of balls disposed therebetween, tongue means on eachkey member positioned for movement between individual balls uponmovement of the key to the depressed position, the dimensions of saidchannel, its stop means and said balls being such that only one tonguemeans can fit between the balls at a time.
 10. Apparatus as defined inclaim 3 wherein each of said photosensitive semiconductor devices is aphototransistor which is a part of a respective bistable flip-flopcircuit and which causes the respective flip-flop circuit to assume itsset condition when the respective light beam is interrupted upondepression of a key; and wherein means are provided for generating areset pulse for said flip-flop circuits.
 11. Apparatus as in claim 10including means for blocking the unoperated key means in response to theoutput signal of the set flip-flop circuit.
 12. Apparatus as defined inclaim 1 in which the machine code system uses six digits and there aresix light beams and six output signal-producing means.